An optical sensor is known, for example, from European patent application EP 2 306 145 A1. This optical sensor comprises a transmitting unit for emitting light rays and a receiving unit comprising a matrix-type array of receiving elements. The light rays are projected in the form a line of light onto an object structure to be detected and are subsequently imaged on the receiving unit. A distance profile for the object structure can be determined in an evaluation unit by evaluating the signals received at the receiving elements and by using the triangulation principle. In the evaluation unit, at least one evaluation window is generated which encompasses in one direction a local region extending along the line of light and in a second direction a distance range. Binary state information is generated by evaluating the number of object points that are located within the evaluation window.
An extensive monitoring area can be scanned with this optical sensor and the line-shaped projection of the light rays emitted by the transmitting unit, wherein it is advantageous that no moving parts are required in this case for deflecting the light rays. Instead, the transmitting unit generates a constant line of light on an object structure to be examined, thus making it possible to detect several objects simultaneously with the optical sensor according to the known system.
Distance information for the objects to be detected is obtained with the aid of the distance measurement that is realized with the triangulation principle. As a result, objects can be detected with local resolution, wherein contour information of objects in particular can be obtained.
By presetting one or several evaluation windows, different objects or object structures can purposely be detected therein. The evaluation windows in this case represent specific segments of the monitoring area, wherein each evaluation window furthermore comprises a defined distance range. The local resolution during the object detection can be predetermined specifically for the respective evaluation windows by presetting this distance range, thus permitting a targeted detection of objects in front of background structures.
Along with the generating of binary state information for each evaluation window, a statement is obtained for each evaluation window on whether or not an expected object structure or an expected object is detected. On the one hand, this evaluation results in the secure and precise detection of an object. On the other hand, it achieves a reduction in data by generating the binary state information from a plurality of object points, so that the evaluation requires only short computing times.
The evaluation of the object points located in an evaluation window is thus generally restricted to counting operations only.